A new technique for the measurement and assessment of carotid artery wall vibrations using ultrasound RF echoes

Abstract

Atherosclerosis is known as the leading cause of heart attacks and brain strokes. One of the symptoms ofthis disease is the reduction of artery wall motion caused by age. This study presents a novel method to extract highfrequency components of wall motion, wall vibrations, based on discrete wavelet transform. The fractal dimension, largestLyapunov exponent, and spectral entropy are then analyzed to indicate the chaotic behavior in wall vibrations. Phaseinformation from demodulated radiofrequency signals is extracted and the entropy of phase-difference is computed as astatistical measure for better characterization of the artery wall tissue. The results show that these features correlatewith age (P < 0.001) and also increase with age. The phase-difference entropy also shows significant correlation withage (r = 0.34, P < 0.001). The measurement results indicate that while age increases, vibrations of the artery wallare irregular and represent chaotic behavior. Our results raise hopes that the proposed approach may be effective indiagnosing atherosclerosis.